« previous next »
Pages: [1]

Author Topic: Chain's a bit slack  (Read 4281 times)

Noodley

Chain's a bit slack
« on: 07 February, 2009, 04:28:25 pm »
Apart from running the risk of ridicule on the forum, what are the hazards and/or problems (if any) associated with having a slack chain?

Logged

Manotea

  • Where there is doubt...
Re: Chain's a bit slack
« Reply #1 on: 07 February, 2009, 04:38:50 pm »
Slackness increases the probability the chain will come off your transmission and cause you to come to a juddering halt. If you are bouncing down a descent at 50kph/180rpm then, well, best case scenario is you will need to lie down for a few minutes whilst you wait for A MASSIVE DOSE OF ADRENALINE to wear off. Apparently.
Logged

rogerzilla

  • When n+1 gets out of hand
Re: Chain's a bit slack
« Reply #2 on: 07 February, 2009, 06:41:12 pm »
If you're on a velodrome and race pace and your chain falls off the sprocket it reportedly takes you three laps to stop.
Logged
Hard work sometimes pays off in the end, but laziness ALWAYS pays off NOW.

Deano

Re: Chain's a bit slack
« Reply #3 on: 07 February, 2009, 06:53:43 pm »
It nearly happened to me the other week, when I felt the chain being forced back onto the teeth of the chainring at about 25 mph.  I'd also experienced it jumping teeth on the sprocket when I was setting off from traffic lights.  That chain was very slack indeed.

I've never (yet) had a chain fall off.
Logged

Chris N

Re: Chain's a bit slack
« Reply #4 on: 07 February, 2009, 07:06:41 pm »
It annoys me when I can feel the slack in the chain when riding downhill, so I keep mine nice'n'tight.
Logged

teethgrinder

Re: Chain's a bit slack
« Reply #5 on: 07 February, 2009, 07:10:16 pm »
If it comes off and wraps around your wheel, you could get into trouble. It could cost you a wheel, paint job, frame or chainset. Even your life if you're really unlucky.
Best to keep your chain tight, but not really tight.
Logged

Wendy

Re: Chain's a bit slack
« Reply #6 on: 07 February, 2009, 08:14:29 pm »
Logged
Your Royal Charles are belong to us.

Crumbling Nick

Re: Chain's a bit slack
« Reply #7 on: 08 February, 2009, 12:19:32 am »
Slack chains are more likely to derail. This only seems to happen at high cadence, which is not the best time to choose. There are 4 ways the chain can come off; 2 are usually harmless, the other 2 can be life-threatening. The harmless modes are more than a tad disconcerting IME. There is some graphic detail of the others in the FAQs.

Overtight chains will cause premature (aka rapid) bearing failure in one or both of the bottom bracket & rear hub.

I don't think that this was considered to be a big issue 40 years ago, though I was never a "club rider" so may have missed some of the lore. Be that as it may, the bushed (mostly Reynolds) chains in those days were less flexible sideways and so less likely to fall off than modern bushingless chains. Doubtless 1/8" chains are/were better than 3/32" in this respect.

We are not (yet?) very good at providing reliable quantitative guidelines as to how slack a chain can safely be, and (me too) tend towards caution. It's not a field which lends itself to controlled experimentation (aka science), for obvious reasons. But it still looks like a culture which is not yet technically mature.

OTOH my chainring is so worn that if there isn't any slack between propulsion & braking, then I worry that the chain's too tight ;) .
Logged

αdαmsκι

  • Instagram @ucfaaay Strava @ucfaaay
  • Look haggard. It sells.
Re: Chain's a bit slack
« Reply #8 on: 08 February, 2009, 12:53:51 pm »
In addition to the problem of the chain coming off, you also get a really annoying jolt / jump feeling when you go from accelerating to leg breaking.
Logged
What on earth am I doing here on this beautiful day?! This is the only life I've got!!

https://tyredandhungry.wordpress.com/

giropaul

Re: Chain's a bit slack
« Reply #9 on: 09 February, 2009, 08:24:07 am »
We've been here before, but in my view:

1) 1/8  chain is made to run in a straight line i.e little lateral slack. 3/32 chain is made to run out of line  i.e. with lateral slack. Therefore trackies use 1/8 in general.

2) Good quality rings and sprockets are more round

3) Too tight a chain is prone to breaking

4) to check if a chain is tight enough (but with some movement say 1 cm up and down) spin the pedals and hold the bike horizontal to the floor and shake it. If it doesn't come off then it won't/can't when you are riding.
Logged

Charlotte

  • Dissolute libertine
  • Here's to ol' D.H. Lawrence...
    • charlottebarnes.co.uk
Re: Chain's a bit slack
« Reply #10 on: 09 February, 2009, 09:28:22 am »
My test for slackness:  If there's any way I can derail the chain with my thumbs when the bike's up on the workstand, then it's too slack.

This method has the advantage that different chain/sprocket combinations will derail more easily than others.  If the chain can't be brought off in this manner, it won't come off when your knees are going like a blender at 180rpm.

Too tight, though - and you'll mash your sprockets, graunch your bearings and make life a lot more hard work.

Nobody said riding a fixie was easy  ::-)
Logged
Commercial, Editorial and PR Photographer - www.charlottebarnes.co.uk

border-rider

Re: Chain's a bit slack
« Reply #11 on: 09 February, 2009, 11:48:20 am »
Tight enough that there's no play* in the transmission, but not so tight that it binds when you turn the pedals.

*this is do-able with good quality concentric components.  Cheaper/more knackered stuff will bind when there's still play, and then it's a compromise.
Logged

Craig

Re: Chain's a bit slack
« Reply #12 on: 09 February, 2009, 01:05:05 pm »
Quote from: Charlotte on 09 February, 2009, 09:28:22 am
My test for slackness:  If there's any way I can derail the chain with my thumbs when the bike's up on the workstand, then it's too slack.
I think its safer to do this using an allen key or similar, to avoid the risk of getting thumbs sliced off by a spinning chain...
There's pictures on Sheldon Brown's site of the possible result: Fixed  Gear  Bicycles  for  the  Road
Logged

Greenbank

Re: Chain's a bit slack
« Reply #13 on: 09 February, 2009, 01:08:17 pm »
Or, more simply, by not spinning the cranks when trying to see if the chain can come off...
Logged
"Yes please" said Squirrel "biscuits are our favourite things."

Chris N

Re: Chain's a bit slack
« Reply #14 on: 09 February, 2009, 01:16:36 pm »
Agreed.  Getting bits of finger stuck in the chain really, really f*cking hurts.
Logged

Charlotte

  • Dissolute libertine
  • Here's to ol' D.H. Lawrence...
    • charlottebarnes.co.uk
Re: Chain's a bit slack
« Reply #15 on: 09 February, 2009, 01:32:49 pm »
Quote from: Craig on 09 February, 2009, 01:05:05 pm
Quote from: Charlotte on 09 February, 2009, 09:28:22 am
My test for slackness:  If there's any way I can derail the chain with my thumbs when the bike's up on the workstand, then it's too slack.
I think its safer to do this using an allen key or similar, to avoid the risk of getting thumbs sliced off by a spinning chain...
There's pictures on Sheldon Brown's site of the possible result: Fixed  Gear  Bicycles  for  the  Road

I'm all too aware of the potential for de-thumbing during this maneuver.  What I'm suggesting is much like when we pop the timing chain off the Santana.  Wind the pedals very slowly, move the chain over to one side.  In the case of the fixie - if you can get it off, it's way too slack.
Logged
Commercial, Editorial and PR Photographer - www.charlottebarnes.co.uk

ChrisO

Re: Chain's a bit slack
« Reply #16 on: 09 February, 2009, 04:20:18 pm »
Someone once showed me a method for tightening the chain which I think finds the necessary balance between tight and slack.

Pull the chain side nut back as far as it will go and tighten, not fully but enough to hold it. Then pull the other side and tighten it the same way. The chain is now too tight and the wheel will be slightly off line.

If you then release the chain side slightly it will pop back to put the wheel in line and with the chain slightly eased.

Logged

Blue Manc

Re: Chain's a bit slack
« Reply #17 on: 09 February, 2009, 07:45:18 pm »
I don't doubt it happens, but how/why would a too tight chain ruin BB, sprocket, rear hub bearings ?
Logged

Noodley

Re: Chain's a bit slack
« Reply #18 on: 09 February, 2009, 09:29:29 pm »
Sounds as if I'd best get my chain so it's not a bit slack (nor too tight)...
Logged

teethgrinder

Re: Chain's a bit slack
« Reply #19 on: 09 February, 2009, 09:47:20 pm »
Ohhhh,

The Grand ol' Duke of YACF, (or should that be AUK? rhymes with York)
He had a fixed wheel bike,
His chain was very very slack,
So he tightened it up again,
And when it was slack, it was slack,
And when it was tight, it was tight,
And when it was neither slack nor tight,
It was about just right.
 ;D
Logged

Robbo5

Re: Chain's a bit slack
« Reply #20 on: 10 February, 2009, 01:17:31 pm »
Quote from: Noodley on 09 February, 2009, 09:29:29 pm
Sounds as if I'd best get my chain so it's not a bit slack (nor too tight)...
The advice on the old Renold leaflets, was "not drum tight, neither too slack..."
My father's recollection from when 3/32" chains and sprockets first came into use was that 3/32" chains seemed to  come off less often.
Logged
Pages: [1]
« previous next »